Information about Zone Melting
Zone melting is a method of separation by melting in which a molten zone traverses a long ingot of impure metal or chemical. In its common use for purification, the molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot. The impurities concentrate in the melt, and are moved to one end of the ingot.
This process is also known as the Float zone process, particularly in semiconductor materials processing.
Zone refining was developed by Bill Pfann in Bell Telephone Laboratories as a method to prepare high purity materials for manufacturing transistors. Its early use was on germanium for this purpose, but it can be extended to virtually any solute-solvent system having an appreciable concentration difference between solid and liquid phases at equilibrium.
In zone refining, solutes are segregated at one end of the ingot in order to purify the remainder, or to concentrate the impurities for analytical or other purposes. In zone leveling, the objective is to distribute solute evenly throughout the purified material, which may be sought in the form of a single crystal. For example, in the preparation of a transistor or diode semiconductor, an ingot of germanium is first purified by zone refining. Then a small amount of antimony is placed in the molten zone, which is passed through the pure germanium. With the proper choice of rate of heating and other variables, the antimony can be spread evenly through the germanium. This technique is also used for the preparation of silicon for use in computer chips.
Another related process is zone remelting, in which two solutes are distributed through a pure metal. This is important in the manufacture of semiconductors, where two solutes of opposite conductivity type are used. For example, in germanium, pentavalent elements of group V such as antimony and arsenic produce negative (n-type) conduction and the trivalent elements of group III such as aluminium and boron produce positive (p-type) conduction. By melting a portion of such an ingot and slowly refreezing it, solutes in the molten region become distributed to form the desired n-p and p-n junctions.
A variety of heaters can be used for zone melting, with their most important characteristic being the ability to form short molten zones that move slowly and uniformly through the ingot. Induction coils, ring-wound resistance heaters, or gas flames are common methods. Another method is to pass an electric current directly through the ingot while it is in a magnetic field, with the resulting magnetomotive force carefully set to be just equal to the weight in order to hold the liquid suspended. Zone melting can be done as a batch process, or it can be done continuously, with fresh impure material being continually added at one end and purer material being removed from the other, with impure zone melt being removed at whatever rate is dictated by the impurity of the feed stock.
In Solar cells Float Zone processing is particularly useful because the single crystal Silicon grown has some very nice properties. The bulk lifetime of carriers in FZ Silicon is the highest among various manufacturing processes. FZ lifetimes are around 1000 microseconds compared to 20-200 microseconds with Czochralski, and 1-30 microseconds with cast multi crystalline Silicon. A longer bulk lifetime increases the efficiency of Solar cells significantly.
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An electric heater is an electrical appliance that converts electrical energy into heat. The heating element inside every electric heater is simply an electrical resistor, and works on the principle of Joule
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This process is also known as the Float zone process, particularly in semiconductor materials processing.
Zone refining was developed by Bill Pfann in Bell Telephone Laboratories as a method to prepare high purity materials for manufacturing transistors. Its early use was on germanium for this purpose, but it can be extended to virtually any solute-solvent system having an appreciable concentration difference between solid and liquid phases at equilibrium.
In zone refining, solutes are segregated at one end of the ingot in order to purify the remainder, or to concentrate the impurities for analytical or other purposes. In zone leveling, the objective is to distribute solute evenly throughout the purified material, which may be sought in the form of a single crystal. For example, in the preparation of a transistor or diode semiconductor, an ingot of germanium is first purified by zone refining. Then a small amount of antimony is placed in the molten zone, which is passed through the pure germanium. With the proper choice of rate of heating and other variables, the antimony can be spread evenly through the germanium. This technique is also used for the preparation of silicon for use in computer chips.
Another related process is zone remelting, in which two solutes are distributed through a pure metal. This is important in the manufacture of semiconductors, where two solutes of opposite conductivity type are used. For example, in germanium, pentavalent elements of group V such as antimony and arsenic produce negative (n-type) conduction and the trivalent elements of group III such as aluminium and boron produce positive (p-type) conduction. By melting a portion of such an ingot and slowly refreezing it, solutes in the molten region become distributed to form the desired n-p and p-n junctions.
A variety of heaters can be used for zone melting, with their most important characteristic being the ability to form short molten zones that move slowly and uniformly through the ingot. Induction coils, ring-wound resistance heaters, or gas flames are common methods. Another method is to pass an electric current directly through the ingot while it is in a magnetic field, with the resulting magnetomotive force carefully set to be just equal to the weight in order to hold the liquid suspended. Zone melting can be done as a batch process, or it can be done continuously, with fresh impure material being continually added at one end and purer material being removed from the other, with impure zone melt being removed at whatever rate is dictated by the impurity of the feed stock.
In Solar cells Float Zone processing is particularly useful because the single crystal Silicon grown has some very nice properties. The bulk lifetime of carriers in FZ Silicon is the highest among various manufacturing processes. FZ lifetimes are around 1000 microseconds compared to 20-200 microseconds with Czochralski, and 1-30 microseconds with cast multi crystalline Silicon. A longer bulk lifetime increases the efficiency of Solar cells significantly.
See also
Ingot is a metal that is solid moulded into simple shape, similar to the final product. It requires a second procedure of shaping, by means of cold/hot working to produce the final product. They involve relatively simple procedures.
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Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) is part of the research and development organization of Alcatel-Lucent and previously the United States Bell System.
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A transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. The transistor is the fundamental building block of the circuitry in computers, cellular phones, and all other modern electronic devices.
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Germanium (IPA: /dʒə(r)ˈmeɪniəm/) is a chemical element in the periodic table that has the symbol Ge and atomic number 32.
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This article is about chemical solutions. For other uses, see Solution (disambiguation).
In chemistry, a solution is a homogeneous mixture composed of two or more substances...... Click the link for more information.
A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. The most common solvent in everyday life is water. Most other commonly-used solvents are organic (carbon-containing) chemicals. These are called organic solvents.
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CRYSTAL is a quantum chemistry ab initio program, designed primarily for calculations on crystals (3 dimensions), slabs (2 dimensions) and polymers (1 dimension) using translational symmetry, but it can be used for single molecules.[1] It is written by V.R. Saunders, R.
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diode is a component that restricts the directional flow of charge carriers. Essentially, a diode allows an electric current to flow in one direction, but blocks it in the opposite direction. Thus, the diode can be thought of as an electronic version of a check valve.
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A semiconductor is a solid that has electrical conductivity in between that of a conductor and that of an insulator, and can be controlled over a wide range, either permanently or dynamically.[1] Semiconductors are tremendously important in technology.
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3, 5
Electronegativity 2.05 (scale Pauling)
Ionization energies
(more) 1st: 834 kJmol−1
2nd: 1594.9 kJmol−1
3rd: 2440 kJmol−1
Atomic radius 145 pm
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Electronegativity 2.05 (scale Pauling)
Ionization energies
(more) 1st: 834 kJmol−1
2nd: 1594.9 kJmol−1
3rd: 2440 kJmol−1
Atomic radius 145 pm
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Silicon (IPA: /ˈsɪlɪkən/ or /ˈsɪlɪˌkɑn/, Latin: silicium
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integrated circuit (also known as IC, microcircuit, microchip, silicon chip, or chip) is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as well as passive components) that has been manufactured in the surface of a
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In the periodic table Group V covers what are now called
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- Group 15 elements: Nitrogen (N), Phosphorus (P), Arsenic (As), Antimony (Sb), Bismuth (Bi), and Polonium (Po)
- Group 5 elements: Vanadium (V), Niobium (Nb), and Tantalum (Ta).
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3, 5
(mildly acidic oxide)
Electronegativity 2.18 (scale Pauling)
Ionization energies
(more) 1st: 947.0 kJmol−1
2nd: 1798 kJmol−1
3rd: 2735 kJmol−1
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(mildly acidic oxide)
Electronegativity 2.18 (scale Pauling)
Ionization energies
(more) 1st: 947.0 kJmol−1
2nd: 1798 kJmol−1
3rd: 2735 kJmol−1
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In the periodic table Group III covered what are now called
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- Group 13 elements: boron (B), aluminium (Al), gallium (Ga), indium (In), thallium (Tl)
- Group 3 elements: scandium (Sc) and yttrium (Y) plus the Lanthanide and Actinide series elements.
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Aluminium (IPA: /ˌæljʊˈmɪniəm/, /ˌæljəˈmɪniəm/) or aluminum (IPA: /əˈluːmɪnəm/
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Boron (IPA: /ˈbɔːrɒn/) is a chemical element with atomic number 5 and the chemical symbol B. A trivalent compound containing boron occurs abundantly in the ore borax.
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An Induction coil or "spark coil" (archaically known as a Ruhmkorff coil) is a type of disruptive discharge coil. It is a passive electrical device used to produce high-voltage pulses from a low-voltage DC supply.
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For the album by Roger Taylor, see .
An electric heater is an electrical appliance that converts electrical energy into heat. The heating element inside every electric heater is simply an electrical resistor, and works on the principle of Joule
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Electric current is the flow (movement) of electric charge. The SI unit of electric current is the ampere (A), which is equal to a flow of one coulomb of charge per second.
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Definition
The amount of electric current (measured in amperes) through some surface, e.g...... Click the link for more information.
magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. Magnetic fields surround electric currents, magnetic dipoles, and changing electric fields.
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Magnetomotive force is any physical cause that produces magnetic flux. It is analogous to electromotive force or voltage in electricity.
In this context, the word "force" is used in a general sense of "that which has a physical effect", and is not the same as mechanical
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In this context, the word "force" is used in a general sense of "that which has a physical effect", and is not the same as mechanical
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A solar cell or photovoltaic cell is a device that converts light energy into electrical energy. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight, while the term photovoltaic cell
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The Czochralski process is a method of crystal growth used to obtain single crystals of semiconductors (e.g. silicon, germanium and gallium arsenide), metals (e.g. palladium, platinum, silver, gold), salts and some man made, (or "lab") gemstones.
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A solar cell or photovoltaic cell is a device that converts light energy into electrical energy. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight, while the term photovoltaic cell
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Fractional freezing is a process used in process engineering and chemistry to separate two liquids with different melting points. It can be done by partial melting of a solid, for example in zone refining of silicon or metals, or by partial crystallization of a liquid, for example
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Freeze distillation is a term for a process of enriching a solution by partially freezing it and removing frozen material that is poorer in the dissolved material than is the liquid portion left behind.
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